1. Field
The present invention relates to electronic devices such as navigation devices, portable MP3 players, portable DVD players, and the like, and, more particularly, to a device, system, and method for selecting a frequency for personal-use FM transmission.
2. Description of the Related Art
Personal-use FM (Frequency Modulation) transmitters are used for transmitting audio information to external audio systems such as home stereo systems or automobile audio systems. This permits the audio information to be played with greater sound quality than would be possible with the electronic device alone. For example, personal-use FM transmitters are often used with portable electronic devices such as MP3 players, portable DVD players, and portable navigation devices for transmitting audio information to an automobile audio system.
In such uses, the personal-use FM transmitter and the FM receiver of the external audio system must be tuned to the same radio frequency or channel to permit audio information to be transmitted between the devices. Ideally, this common channel should not interfere with the broadcast frequencies of other transmitters such as FM radio station transmitters, Traffic Message Channel (TMC) transmitters, or the like.
Personal-use FM transmitters and the external audio systems to which they transmit are typically tuned in one of two ways. In a first way, a personal-use FM transmitter is pre-set to a particular frequency during manufacture or installation so that it always transmits over the same frequency. A corresponding receiver of an external audio system is then manually tuned to the same pre-set frequency. The selected frequency is usually near the bottom of the FM frequency spectrum, because these frequencies are rarely used by private radio stations. However, many universities and other public radio stations are now transmitting on these lower FM frequency channels, thus interfering with the pre-set frequencies of many personal-use FM transmitters. A second way of tuning requires a user to randomly select a transmission frequency and then manually tune both the personal-use FM transmitter and the FM receiver of the external audio system to the selected frequency. The user then listens to the speakers of the external audio system to ensure that the selected frequency does not interfere with other received transmissions. If it does, the user must repeat these steps until an available frequency is found. This process is time-consuming and frequently fails to find a transmission frequency without interference.
Consequently, it would be desirable to provide a personal-use FM transmitter capable of allowing a user to more efficiently and accurately selecting a frequency for personal-use FM transmission.